/*
Code by @marlov
*/
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <utility>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <iterator>
using namespace std;
typedef long long ll;
typedef pair<long long,long long> pi;
#define maxN 10000000
long long dpfront[maxN],dpback[maxN];
long long delivery(int N,int K,int L,int position[]){
long long ci=0;
while(position[ci]==0){
ci++;
N--;
}
long long pos[N];
for(long long i=0;i<N;i++){
pos[i]=position[i+ci];
//cout<<i-ci<<" with "<<pos[i-ci]<<'\n';
}
for(long long i=0;i<N;i++){
if(i<K) dpfront[i]=min((ll)L,2*pos[i]);
else dpfront[i]=min((ll)L,2*pos[i])+dpfront[i-K];
}
for(long long i=0;i<N;i++){
if(i<K) dpback[i]=min((ll)L,2*(L-pos[N-i-1]));
else dpback[i]=min((ll)L,2*(L-pos[N-i-1]))+dpback[i-K];
}
/*
for(long long i=0;i<N;i++){
cout<<dpfront[i]<<" and "<<dpback[i]<<'\n';
}
*/
long long result=min(dpback[N-1],dpfront[N-1]);
for(long long i=1;i<=N-1;i++){
//cout<<"This checks: "<<dpfront[i-1]<<" and "<<dpback[N-i-1]<<'\n';
result=min(dpfront[i-1]+dpback[N-i-1],result);
}
return result;
}
